File Inspector

What this tool does

This tool tells you the key facts about any file: its name, size, type, when it was last changed, and a SHA-256 fingerprint of its contents. Drop in a file and it reports all of it at once, in your browser, with nothing uploaded.

How to use it

1. Drop a file onto the drop zone, or click to select one. Any file type works.
2. Press Inspect.
3. Read the details that appear. Reset clears it for another file.

How it works

The tool reads the properties your browser already knows about the file, its name, size, type, and modified date, and then computes a SHA-256 hash of the file's contents using your browser's built-in cryptography. All of it happens on your device, so the file is never uploaded, which matters when you want to fingerprint something private.

What the details mean

Most of the report is straightforward, but each piece has its uses. The name and size are self-explanatory, with the size shown in readable units. The MIME type is the file's category as the browser understands it, like image/png or application/pdf, useful for confirming a file really is what its extension claims; it may show as blank when the type cannot be determined. The last modified date is when the file was last changed, as recorded on your system. Handy as those are, the fingerprint is the part worth understanding properly.

The SHA-256 fingerprint, and why it is useful

A SHA-256 hash is a fixed-length string of characters calculated from a file's exact contents. Its key property is sensitivity: change a single byte anywhere in the file and the hash changes completely. That makes it a reliable fingerprint, two files with the same hash have identical contents, and any difference at all produces a different hash.

This turns out to be genuinely useful. When you download software or an important file, the source often publishes its SHA-256 hash, and checking that your copy produces the same hash confirms two things at once: that the file downloaded without corruption, and that it has not been tampered with along the way. The same trick lets you check whether two files are truly identical without opening them, or verify that a file has not changed since you last saw it. Because this tool computes the hash locally, you can do all of that even with confidential files, since nothing leaves your device. To strip identifying details from a PDF before sharing, the PDF Metadata Remover handles that, and the Zip Extractor opens archives.

Questions people ask